What is creating smudging in my render?
When dealing with glass you need the object to have some thickness.
To illustrate the issue with two identical glasses:



The glass on the right has only a subsurf modifier, you can clearly see a lot of artifacts as white and black bands. The one on the left has a Solidify modifier before the subsurf. The glass looks much cleaner and realistic, and you don't need that many samples (This image was rendered with only 100 samples)